1. Field of the Invention
The present invention relates to a dielectric ceramic composition available to be sintered at a low temperature having low specific permittivity, and a multilayer type electronic device such as a multilayer complex electronic device, a multilayer common mode filter, a multilayer ceramic coil and a multilayer ceramic capacitor and the like wherein a dielectric ceramic composition as a dielectric layer is applied.
2. Description of the Related Art
In recent years, with a demand for reduction in size, for high performance and high frequency on an electronic device such as a cell phone and the like used in a communication field, a demand for LC complex electronic device, a common mode filter and the like having high attenuation characteristic at high frequency region is rapidly increased.
At present, Ni—Cu—Zn-based ferrite as a magnetic substance or Cu—Zn-based ferrite as a non-magnetic substance is used for a coil portion of LC complex electronic device or a common mode filter. However, effect of stray capacitance tends to be received by above material, because a specific permittivity of above material is about 15, which is comparatively high. Therefore, there is a limit for responding to the high frequency, thus, a material having further low specific permittivity is required. Also, for further high performance, a material having f·Q value and high dielectric resistance is required.
Such the LC complex electronic device, a common mode filter, a multilayer type LC complex device having a common mode are formed by cofiring different materials (for example, a capacitor portion and a coil portion). Therefore, it is necessary that coefficients of linear expansion of different materials should be conformed as far as possible. Also, for reducing cost and a direct current resistance of a conducting material, it is preferable to use a conducting material including Ag, it is required that a material which can be sintered at lower temperature less than a softening point of Ag (for example, 950° C. or lower) too.
For example, Japanese Patent Gazette No. 3030557 disclosed a dielectric ceramic material wherein 1 to 30 parts by weight of CuO, 0.6 to 5 parts by weight of manganese oxide calculated as a conversion of MnO, as low temperature firing additives, are added to 100 parts by weight of MgO.SiO2 (MgO/SiO2:mol ratio=1.0 to 2.0) so as to be a base material, 5 to 200 parts by weight of glass is added to 100 parts by weight of the base material.
However, in the Japanese Patent Gazette No. 3030557, the added glass is mainly PbO-based glass, using thereof tends to be not recommended from a problem of an environment burden in recent years.
Also, in Japanese Patent Laid Open Nos. 2001-247359, 2002-29826 and 2002-29827, dielectric ceramic compositions wherein a specific permittivity is relatively low and a Q-value is relatively high are disclosed. However, because a glass component included in the dielectric ceramic compositions disclosed in the above documents is large amount, there is a problem of reduction in reliability. In specific embodiments of the above documents, there are lots of samples whose sintering temperature is 1000° C. or higher, it is insufficient to make possible to sinter at a low temperature (for example, 950° C. or lower). Further, coefficients of linear expansion of samples of the embodiments are 10 ppm/° C. and the like, there was a problem that co-firing with materials having various coefficients of linear expansion.
In Japanese Patent Laid Open No. 2003-95746, a dielectric ceramic composition having relatively low specific permittivity and relative high Q-value is disclosed. However, because a glass component included in the dielectric ceramic compositions disclosed in the above document is large amount, there is a problem of reduction in reliability. Also, coefficients of linear expansion of samples of embodiments are not disclosed, thus, it was unclear as to whether it is possible to respond for cofiring with materials having various coefficients of linear expansion.
In WO2005/082806, a dielectric ceramic material wherein a borosilicate glass is added to a forsterite and a calcium titanate is disclosed. However, in the WO2005/082806, because coefficients of linear expansion of samples of embodiments are not disclosed, thus, it was unclear as to whether it is possible to respond for cofiring with materials having various coefficients of linear expansion.